trepetti Posted June 28, 2015 Share Posted June 28, 2015 ...at least I THINK its fueling... No CEL, just a real stumble when going from off-throttle to on-throttle below 3k rpm, but most prominent in the 1.5 to 2k range, typical traffic-jam driving. I did a little analysis with Torque app, and I see the short term fuel trim go from 0 off-idle to nearly -10 as the throttle opens. This is where the stumble seems to be. Then, the trim swings to + 5 ish and everything seems ok. So I am suspecting the forward O2 sensor, but I don't know how to troubleshoot the sensor to try to confirm or dispel my theory. So questions are: 1 - Do you think I am looking in the right direction? If anyone has a suggestion on alternatives please let me know. 2 - Does anyone have suggestions on how to see if my O2 sensor needs replacement? Thanks Link to comment Share on other sites More sharing options...
JmP6889928 Posted June 29, 2015 Share Posted June 29, 2015 Front O2 Sensor-change it with either a known good used unit or Subaru OE only. I would be about 90% that it will cure the problem. They go bad and do a lot of weird things and don't generally set CEL AND they really screw up STFT when they start to go bad. Good luck. Link to comment Share on other sites More sharing options...
trepetti Posted June 29, 2015 Author Share Posted June 29, 2015 Front O2 Sensor-change it with either a known good used unit or Subaru OE only. I would be about 90% that it will cure the problem. They go bad and do a lot of weird things and don't generally set CEL AND they really screw up STFT when they start to go bad. Good luck. I figured the sensor was bad, but I was hoping to figure some way to test the theory instead of guessing. Thanks for the advice and I'll look for a replacement. Do you think an OEM is better than a Bosch? ....and I realize that the question is only for your opinion. Link to comment Share on other sites More sharing options...
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